Vacuum fluorescent displays with a driver IC (also referred to below as CIG-VFDs) can have a driver IC mounted inside the vacuum fluorescent display, and are therefore capable of a reduced package size, as well as high density and display capacity.
A filament support provided to a metal cover of an IC shield is known in the prior art as an example of a filament support structure of a CIG-VFD (Unexamined Utility Model Application Publication No. 1-46948). Examples (Patent Reference 2, Patent Reference 3) are also known in which the filament support is provided separately from the metal IC shield to an end part of a metal frame whereon a metal IC shield for shielding the driver IC is mounted (Unexamined Utility Model Application Publication No. 5-36741, Japanese Laid-open Patent Application Publication No. 6-51335).
There has been demand in recent years for a higher-definition dot pitch in full-dot-type graphic CIG-VFDs. The graphic CIG-VFDs generally employ a dynamic scan drive as a drive method. However, when a high definition is reached wherein the pixel pitch of the display unit is at a level of 0.325 mm, the grid cut-off voltage effect increases, and light and dark parts become markedly more noticeable in comparison with a roughly pixilated display at a pixel pitch level of 0.65 mm. It is known that the distance between a grid and an anode substrate can be reduced in order to solve this problem, but a problem has been encountered in the prior art in that reducing this distance leads to a decrease in display luminance and a loss of display quality.
Accordingly, in order to prevent a decrease in display luminance, an arrangement has been considered wherein the distance between a filamentary cathode and a phosphor on the anode substrate is reduced by setting the distance between the filamentary cathode and the grid to be shorter than in a conventional product.